Infrared switching electrochromic devices based on tungsten oxide

Abstract

Different types of electrochromic devices for thermal emittance modulation were developed in the spectral region from mid-to far-infrared ͑2-40 m͒. In all devices polycrystalline and amorphous tungsten oxide have been used as electrochromic and ion storage layer, respectively. Two types of all-solid-state devices were designed, one with a metal grid for the top and bottom electrode deposited on a highly emissive glass substrate, and another with a top metal grid electrode and a highly reflecting bottom metal electrode layer. Tantalum oxide is used as an ion conductor in both device types. The third device type consists of a polymeric ion conductor. All solid-state constituent layers were grown by either reactive or nonreactive dc or rf magnetron sputtering in a high vacuum environment. Modulation of the emittance is accomplished by reversible insertion of Li ions into polycrystalline WO 3 by applying and switching a small voltage across the structure. Spectrally dependent measured reflectance modulation of the device has been used to determine the device emissivity modulation with respect to the blackbody emissivity spectra at 300 K. Best device performance was found in both solid-state devices showing an emissivity modulation of about 20%.

Optical properties of thin films of mixed Ni–W oxide made by reactive DC magnetron sputtering

“…The origin of the Gauss oscillator at 0.4 eV is unknown, although broad mid-IR absorption at somewhat different energies has been observed previously in WO 3 [14,18]. This absorption could be associated with gap states or possibly related to polaronic transitions.…”

Polaron and phonon properties in proton intercalated amorphous tungsten oxide thin films

“…33,35 Previous IRSE focused on uncolored amorphous tungsten oxide and electrochromic device performance for emittance modulation in the IR spectral region. 4,36 Elucidation of the phonon mode properties in connection with the polaron properties is still lacking. Accordingly, no conclusive statement about the source of the polaron cause had been made.…”

Oxygen plasma effects on optical properties of ZnSe films

“…Theoretical device performance was evaluated based on previous experimental device results 33,34 and the optical data on degraded ZnSe layers presented in this article. Details of this performance study are being published elsewhere.…”

“…1. 34 This is potentially useful for thermal control of spacecraft operating at and just above room temperature ͑300-350 K͒. However, there is a serious problem that needs to be solved before electrochromics can be used in space: the optical properties of WO 3 , a major material proposed for use in electrochromic devices, change significantly after exposure to AO.…”

“…was recently developed that operates over the spectral range from 2 to 35 m. [32][33][34] The design of this electrochromic emissivity modulation device is shown in Fig. 1.…”